The manuscript is badly misbound, sharing the misfortune of so many other manuscripts from the collection of Philippe de Béthune, see the reconstruction under Books of Hours and the detailed CHD Guide GkS 1610.
The highest degree of feast is written in blue colour (=Solemne, 12 days including St. Gacianus, bishop of Tours on Dec.18th), other rubricated feasts (=Duplex) are in red as usual. (Compare this calendar with a contemporary calendar for Tours in KB NkS 35 8°). [The calendar is written on folios initially ruled for normal text with 22 lines. Consequently is the month divided after 20 days, and not after the 15th, as usual, which is highly unconventional. The links below to the versosides of the KB Online Facsimile are placed above the 16th - for purely practical reasons]